This invention relates to fabric softening compositions and, in particular, to the compositions in the form of an aqueous emulsion or dispersion.
It has long been recognized that certain chemical compounds have the capability of imparting softness to textile fabrics. These compounds, which are known generally as "softening agents," "fabric softeners," or "softeners," have been used both by the textile industry and by housewives in the laundry to soften a finished fabric, thereby making the fabric smooth, pliable and fluffy to handle. In addition to the quality of softness, the fabrics frequently have a reduced tendency to static cling and are easier to iron.
The softening agents which are usually employed in compositions intended for use by the housewife are cationic surfactant compounds, commonly quaternary ammonium compounds having at least two long alkyl chains, for example distearyl dimethyl ammonium chloride. The positive charge on the softening compound encourages its deposition onto the fabric substrate, the surface of which is usually negatively charged.
However, although the above mentioned cationic compounds are highly effective softeners when applied in a rinse solution, there are certain disadvantages associated with their use. For example, the cationic compounds having long alkyl chains are very sensitive to carry over of anionic detergent into the rinse. Thus, carry over of anionic detergent tends to neutralize the softening effect because the anionic-cationic complex tends to precipitate out of solution. Also, certain cationic surfactant compounds are expensive and in short supply and it is therefore desirable, for commercial reasons, to provide softening compositions having a reduced amount of cationic surfactant compound. Furthermore, softening compositions which comprise predominantly long chain cationic compounds have the disadvantage that the treated fabrics tend to become overloaded with softener and become discolored, greasy or undesirably non-absorbent.
While certain nonionic compounds have been proposed as fabric softening agents, it has been found that these deposit only very inefficiently from aqueous solution because of their lack of positive charge, and in order to obtain effective utilization of such compounds it is necessary to use them in conjunction with an automatic clothes dryer. The relatively high temperature of the drying process assists the nonionic softener compound to spread over the fabric surface as a melt. It has not heretofore been possible to utilize such compounds effectively in a rinse-added softener composition.
It is an object of the present invention to provide softening compositions which employ nonionic softeners and which provide excellent deposition onto the fabric surface from aqueous solution.
This and other objects are achieved by means of a composition which includes nonionic and cationic compounds in specific proportions and is in the form of an aqueous emulsion or dispersion suitable for rinse-added use.